This invention relates to acyclic machines, and more particularly, to such machines utilizing a plurality of liquid metal current collectors providing electrical connections between the rotor and stator members thereof. Such machines include the disk-type acyclic machine described in U.S. Pat. No. 3,585,398, issued June 15, 1971 to L. M. Harvey and assigned to the instant assignee, a disk/drum type acyclic machine as disclosed in my U.S. patent application Ser. No. 898,923, filed Apr. 21, 1978, now U.S. Pat. No. 4,208,600, issued June 17, 1980 and assigned to the instant assignee, and drum-type acyclic machines.
In high current operation of acyclic machines, it is necessary to provide a reliable high current capacity contact between rotor and stator disks. In machines using liquid metal current collectors, this requires a constant supply of liquid metal to the current collectors in order to continuously wet the contact surfaces between rotor and stator disks and bridge the gap between the contact surfaces. At high speeds of operation, the centrifugal force and Lorentz expulsion forces tend to drive the liquid metal from the radially-inner current collectors. If the liquid metal is expelled from said current collectors, the collectors would operate dry, in which condition the current-carrying capacity of the current collectors is inadequate for high current density machines. Severe damage to the current-carrying contact surfaces of the current collectors would quickly follow.
Prior art methods and apparatus for circulating liquid metal in a current collector include that disclosed in my U.S. Pat. No. 4,027,183, issued May 31, 1977 and assigned to the instant assignee, and that disclosed in U.S. Pat. No. 4,027,184, issued May 31, 1977 to Hurley, and assigned to the instant assignee. These disclosures are drawn to localized circulation of liquid metal around a single current collector, and require a large quantity of liquid metal in the gap separating the stator and the rotor. The large quantity of liquid metal required for these current collectors causes large viscous losses due to frictional contact between the rotor surfaces moving relative the liquid metal in contact with the rotor.
A prior art liquid metal supply system employing an external pumping system to provide liquid metal to current collectors is disclosed in U.S. Pat. No. 3,211,936, issued Oct. 12, 1965 to Harvey, and assigned to the instant assignee. Such a technique requires substantial external equipment and connections to the machine to provide a continuous supply of liquid metal.
Still another method of liquid metal circulation is described in my U.S. Pat. No. 3,989,968, issued Nov. 2, 1976, and assigned to the instant assignee. Liquid metal circulation is provided in the vicinity of a single collector ring by liquid metal circulation around an intermediate current collector to provide continuous liquid metal contact between the stator and rotor collector rings.
One technique to provide liquid metal circulation within an acyclic machine is described in my U.S. patent application Ser. No. 924,055, filed July 12, 1978, now U.S. Pat. No. 4,207,486, issued June 10, 1980, and assigned to the instant assignee. In this patent application, kinetic energy imparted to liquid metal within a current collector is converted into pressure by a scoop, which collects a portion of the circulating liquid metal and supplies a pressurized flow of liquid metal from a radially-outer current collector to a radially-inner current collector. A return flow path is provided within the stator disk to maintain continuous circulation of liquid metal within the machine.
The primary object of the instant invention is to provide a method and apparatus to provide an automatic and reliable supply of liquid metal to the current collectors of an acyclic machine at all speeds of operation.
A second object is to provide a reliable supply of liquid metal to current collectors, while employing a minimum quantity of liquid metal in each current collector site, so as to reduce to a minimum the viscous drag losses at high rotational speed.
A further object of the instant invention is to eliminate the necessity for external pumps and related liquid metal conditioning auxiliaries for high speed acyclic generators without introduction of additional moving parts within the machine itself, and without adding substantially to the machine complexity.